Not for the F150 but this is a non vehicle specific question. If you found one bad head gasket on a V-6 or V-8 would you automatically change both, or just the one known bad one ? I am not sure how long I'll keep this one target vehicle, did notice that the anti freeze was neglected and overdue for a change. One side tested normal compression readings, the other had one cylinder close to normal, one at zero, and one down a bit, no metallic sounds like valves hitting pistons, but tear down will reveal if this is true.

Anyways what say you guys, do both sides or only the known bad one ?

 

absolutely do both while it's apart. it's not even a question.

edit: since this may not be for an f series.. If it was some sort of transverse v6, and the front head was the bad side, I'd think real hard before pulling the head on the firewall side, lol.. But I don't buy those types of vehicles in the first place.

 

It's not an issue with front and back it's not a ford but rather a GM, but really same layout as our F150s, so for other folks - they would do the same ?

 

Do both and save yourself the trouble dude. Because i bet money a month later you will pull the intake and everything off for the other side when it blows.